Molecular orbital ordering in titania and the associated semiconducting behavior

RF-sputtered TiOx layers were thermally treated and the associated thin-film transistor properties were studied. X-ray diffraction and x-ray absorption spectroscopy analyses indicate that as-grown amorphous TiOx films crystallize to anatase at temperatures above 450 °C in air. Thin-film transistors incorporating anatase active layers exhibit n-type behavior, with field effect mobility values near 0.11 cm2/Vs when annealed at 550 °C. Such a phenomenon is suggested to originate from the ordering of Ti 3d orbitals upon crystallization, and the mobility enhancement at higher annealing temperatures may be attributed to the reduced grain boundary scattering of carriers by virtue of enlarged average grain size.